Conventional aircraft are known in which the control surfaces of the wing are controlled mechanically by moving a control stick that is mechanically connected to the control surfaces.
Aircraft are also known in which the control surfaces are controlled by electrical and/or hydraulic actuators, which are themselves controlled with the help of sensors for sensing movement of the stick. With such apparatuses, the stick is not mechanically connected to the control surfaces and the user does not feel any resistance from the stick enabling the user to estimate how much the control surfaces have moved and the forces to which they are being subjected. The further a control surface departs from the flow axis of the fluid through which the aircraft is moving, the greater the forces the fluid imparts onto the control surface, thereby tending to remind the pilot that the control surface is off-axis relative to the flow of fluid.
It is therefore desirable in particular on aircraft with electrically and/or hydraulically actuated control surfaces to create return forces on the control stick that are representative of the theoretical position of the control surfaces. Thus, document U.S. Pat. No. 4,580,210 A1 describes a device for generating a return force on an aircraft control stick. The return force is generated by electrical actuators. In the event of those actuators failing, the pilot is deprived of any return force and that can make piloting dangerous.